Fluorinated vinyl ethers, copolymers thereof, and use in lithographic photoresist compositions

ABSTRACT

Fluorinated vinyl ethers are provided having the structure of formula (I) the structure of formula (I) 
                         
wherein at least one of X and Y is a fluorine atom, and L, R 1 , R 2 , R 3 , R 4  are as defined herein. Also provided are copolymers prepared by radical polymerization of (I) and a second monomer that may not be fluorinated. The polymers are useful in lithographic photoresist compositions, particularly chemical amplification resists. In a preferred embodiment, the polymers are substantially transparent to deep ultraviolet (DUV) radiation, and are thus useful in DUV lithographic photoresist compositions. A method for using the composition to generate resist images on a substrate is also provided, i.e., in the manufacture of integrated circuits or the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 10/424,673,filed Apr. 25, 2003, the disclosure of which is incorporated byreference in its entirety.

TECHNICAL FIELD

This invention relates generally to the fields of polymer chemistry,lithography, and semiconductor fabrication. More specifically, theinvention relates to novel monomers capable of undergoing radicalcopolymerization with electron-deficient monomers, to form a copolymersuitable for use in a lithographic photoresist (“resist”) composition,particularly in a chemical amplification photoresist composition, e.g.,a deep-ultraviolet (DUV) photoresist composition.

BACKGROUND OF THE INVENTION

Ongoing efforts are being made in the field of microelectronic devicesto achieve a higher circuit density. One method of increasing the numberof components per chip is to decrease the minimum feature size on thechip, which requires higher lithographic resolution. This wasaccomplished over the years by reducing the wavelength of the imagingradiation from the visible (436 nm) down through the ultraviolet (365nm) to the deep ultraviolet (DUV) at 248 nm. Development of commerciallithographic processes using ultra-deep ultraviolet radiation,particularly 193 nm and 157 nm, has become of significant interest. See,with respect to 193 nm resists, Allen et al. (1995), “Resolution andEtch Resistance of a Family of 193 nm Positive Resists,” J. Photopolym.Sci. and Tech. 8(4):623, and Abe et al. (1995), “Study of ArF ResistMaterial in Terms of Transparency and Dry Etch Resistance,” J.Photopolym. Sci. and Tech 8(4):637.

In order for photoresists to function properly, their films must betransparent enough at the exposing wavelength to enable sufficient lightto penetrate to the bottom of the film to create usable developed reliefimages. This generally corresponds to a maximum absorbance of up toapproximately 0.4 or 0.5 for the required film thickness. The poortransparency at 157 nm of the polymers currently used in 248 nm(primarily p-hydroxystyrene based) and 193 nm resists (polymethacrylatesand norbornene-maleic anhydride co- and terpolymers) is well known andthere is some level of understanding of what types of polymers aretransparent at 157 nm. See Kunz et al. (1999), “Outlook for 157 nmResist Design,” Proc. SPIE 3678, 13. The most transparent materialsidentified to date, heavily fluorinated polymers such aspolytetrafluoroethylene (e.g., Teflon AF®; see Endert et al. (1999)Proc. SPIE-Int. Soc. Opt. Eng, 3618:413) or hydridosilsesquioxanes (seeU.S. Pat. No. 6,087,064 to Lin et al.), are not suitable because they donot have the requisite reactivity or solubility characteristics. Thechallenge in developing chemically amplified resists for 157 nmlithography is in achieving suitable transparency in polymers that canbe developed efficiently using industry standard developers.

Homo- and copolymers of methyl α-trifluoromethylacrylate (MTFMA) havebeen found to be surprisingly transparent at 157 nm, exhibiting anoptical density (OD) of 3/μm, while poly(methyl methacrylate) (PMMA) ishighly absorbing (exhibiting an OD of 5.7/μm at 157 nm). Unfortunately,however, MTFMA is reluctant to undergo radical homopolymerization andhomopolymer can be made only by anionic polymerization. Itsincorporation into copolymers with methacrylates is significantly lessthan 50%. See Ito et al. (1981), “Methyl Alpha-Trifluoromethylacrylate,an E-Beam and UV Resist,” IBM Technical Disclosure Bulletin 24(4):991;Ito et al. (1982), “Polymerization of Methyl α-(Trifluoromethyl)acrylateand α-(Trifluoromethyl)-acrylonitrile and Copolymerization of TheseMonomers with Methyl Methacrylate,” Macromolecules 15:915; Willson etal. (1983), “Poly(methyl α-Trifluoromethylacrylate) as a PositiveElectron Beam Resist,” Polymer Engineering and Science 23(18):1000-1003;Ito et al. (1984) “Radical Reactivity and Q-e Values of Methylα-(Trifluoromethyl)acrylate,” Macromolecules 17:2204; and Ito et al.(1987), “Anionic Polymerization of α-(Trifluoromethyl)Acrylate,” inRecent Advances in Anionic Polymerization, T. E. Hogen-Esch and J. Smid,Eds. (Elsevier Science Publishing Co., Inc.).

Certain norbornene derivatives have been identified as comonomers thatundergo radical copolymerization with α-trifluoromethylacrylic monomers,as described in U.S. Pat. No. 6,509,134 to Ito et al. and in U.S. PatentApplication Publication No. 2002/0102490 A1. In addition, it has beendemonstrated, quite recently, that MTFMA and otherα-trifluoromethylacrylic esters undergo radical copolymerization withvarious vinyl ether derivatives, which has opened up more possibilitiesin the design of 157 nm and 193 nm bilayer and single layer resistmaterials; see, e.g., U.S. patent application Ser. No. 10/091,373 toIto, filed Mar. 4, 2002, for “Copolymer for Use in AmplificationResists,” assigned to International Business Machines Corporation. Vinylethers have been copolymerized with maleic anhydride (MA) for the designof 193 nm resists, as described by Choi et al. (2000), “Design andSynthesis of New Photoresist Materials for ArF Lithography,” Proc. SPIE3999:54. A third functional monomer, however, had to be terpolymerizedwith the vinyl ether and MA because neither the vinyl ether used nor theMA was functionalized. In addition, incorporation of a conventionalvinyl ether into a copolymer does not increase the polymer's polarity,and so does not enhance the efficiency of resist development in industrystandard developers. Furthermore, conventional vinyl ethers do notenhance the 157 nm transparency of a copolymer containing anα-trifluoromethylacrylate co-monomer.

There is, accordingly, a need in the art for new polymers that exhibitenhanced transparency at 157 nm and contain a sufficient number of polargroups so that solubility in industry standard developers, particularlyaqueous base, is improved relative to the solubility of previouslydisclosed polymers used in 157 nm resists.

SUMMARY OF THE INVENTION

In one aspect of the invention, then, a fluorinated vinyl ether isprovided that is capable of undergoing radical polymerization with asecond monomer, e.g., an electron-deficient monomer, to give a copolymerexhibiting good transparency in the DUV and enhanced solubility inindustry standard developers, particularly in aqueous base. Thefluorinated vinyl ether is composed of ethylene directly substituted onan olefinic carbon atom with a moiety —OR* and optionally furthersubstituted on an olefinic carbon atom with one, two, or threeadditional nonhydrogen substituents, wherein R* comprises a fluorinatedalkyl moiety substituted with a protected or unprotected hydroxyl group,and further wherein an atom within R* may be (a) taken together with oneof the additional nonhydrogen substituents, if present, or (b) directlybound to an olefinic carbon atom, to form a ring.

In one embodiment, R* has the structure -L-C(CX₃)(CY₂Z)(OR⁴), such thatthe fluorinated vinyl ether has the structure of formula (I)

wherein:

L is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂ alkylene (e.g.,C₁-C₁₂ fluoroalkylene), C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, C₅-C₁₄ aryl,substituted C₅-C₁₄ arylene (e.g., C₅-C₁₄ fluoroarylene), C₅-C₁₄heteroarylene, substituted C₅-C₁₄ heteroarylene, and combinationsthereof;

X is H or F;

Y is H or F, providing that when X is H, then Y is F;

Z is identical to Y, or is taken together with another substituent toform a ring;

R¹ is selected from H, C₁-C₁₂ alkyl, fluorinated C₁₋₁₂ alkyl, and C₃-C₁₅alicyclic;

R² is selected from H, C₁-C₁₂ alkyl, fluorinated C₁₋₁₂ alkyl, and C₃-C₁₅alicyclic, or R² and one of L and Z are taken together to form a ring,generally a five-membered to nine-membered ring; and

R³ is selected from H, C₁-C₁₂ alkyl, and C₃-C₁₅ alicyclic, or R³ and oneof R¹, L, and Z are taken together to form a ring, generally afive-membered to nine-membered ring;

R⁴ is selected from H, an acid-labile group optionally substituted withone or more fluorine atoms, and an acid-inert moiety optionallysubstituted with one or more fluorine atoms.

In another aspect of the invention, a copolymer is provided that isprepared by copolymerization of a fluorinated vinyl ether as describedabove, e.g., a fluorinated vinyl ether having the structure of formula(I), with a second monomer having the structure of formula (II)

wherein:

R⁵ is selected from F, lower fluoroalkyl, cyano, —(CO)—O—R⁹,—(CO)—NR¹⁰R¹¹, —(CO)—R¹², and —S(O)₂—OR¹³, or is taken together with R⁶or R⁸ to form a ring, generally a five- to nine-membered ring;

R⁶, R⁷, and R⁸ are independently selected from H, F, lower alkyl, lowerfluoroalkyl, cyano, —(CO)—O—R⁹, —(CO)—NR¹⁰R¹¹, —(CO)—R¹², and—S(O)₂—OR¹³, or wherein R⁷ is taken together with R⁶ or R⁸ to form aring, generally a five- to nine-membered ring;

R⁹ is H, an acid-labile moiety optionally substituted with one or morefluorine atoms, or an acid-inert moiety optionally substituted with oneor more fluorine atoms; and

R¹⁰, R¹¹, R¹², and R¹³ are independently selected from H, C₁-C₁₂ alkyl,substituted C₁-C₁₂ alkyl, C₁-C₁₂ heteroalkyl, substituted C₁-C₁₂heteroalkyl, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, C₅-C₁₄ aryl,substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl, and substituted C₅-C₁₄heteroarylene.

The copolymers may be blended with one or more additional polymers, withany such additional polymers generally selected to increase transparencyat a desired wavelength, increase dry etch resistance, and/or improveaqueous base development. Representative additional polymers aredisclosed in U.S. patent application Ser. No. 10/090,646 to Breyta etal., filed Mar. 4, 2002, for “Polymer Blend and Associated Methods ofPreparation and Use,” assigned to International Business MachinesCorporation. A preferred additional polymer contains monomer unitsbearing a fluoroalcohol group, such as NBHFA(bicyclo[2.2.1]hept-5-ene-2-(1,1,1-trifluoro-2-trifluoromethylpropan-2-ol).These preferred polymers may be NBHFA homopolymers (“PNBHFA”) orcopolymers of NBHFA with other monomers, including, without limitation,other norbornene monomers. Copolymer blends of the invention are notlimited in this respect, however, and the invention encompasses blendsof the present copolymers with any suitable polymers.

These copolymers have excellent transparency in the DUV, e.g.,exhibiting an OD that is less than 2.5, preferably less than 2.0, oreven less than 1.5 at 157 nm, depending on the comonomer. The copolymersalso have a lower and controllable glass transition temperature T_(g),in turn providing better adhesion and the possibility of annealing toachieve better environmental stability.

In an additional aspect of the invention, the aforementioned copolymeris incorporated into a photoresist along with a radiation-sensitive acidgenerator. The photoresist so provided will generally, although notnecessarily, contain a dissolution modifying additive (e.g., adissolution inhibitor), a solvent, and at least one additive selectedfrom dyes, sensitizers, stabilizers, acid diffusion controlling agents,surfactants, anti-foaming agents, adhesion promoters, and plasticizers.The photoresist is used in a process for generating a resist image on asubstrate by: (a) coating a substrate with a film of the photoresist;(b) exposing the film selectively to a predetermined pattern ofradiation so as to form a latent, patterned image in the film; and (c)developing the latent image with a developer. The radiation may beelectron-beam, x-ray, or ultraviolet radiation, although radiation inthe DUV, particularly radiation having a wavelength of 157 nm, ispreferred. The photoresist provides higher resolution and betterperformance than previous polymers proposed for use in 157 nm resists.

The invention additionally pertains to a method of forming a patternedmaterial structure on a substrate by: (a) applying a photoresistcomposition of the invention to a substrate surface to form a resistlayer over a material selected from a semiconductor, a ceramic, and ametal; (b) patternwise exposing the resist to radiation whereby acid isgenerated by the radiation-sensitive acid generator in exposed regionsof the resist layer; (c) contacting the resist with a developersolution, whereby the developed regions of the resist layer reveal apatterned resist structure; and (d) transferring the resist structurepattern to the material by etching into said material through spaces inthe resist structure.

The disclosure provides a fluorinated vinyl ether having the structure

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are SEM photos of the patterned resist prepared asdescribed in Example 11, using a 193 nm exposure step.

FIGS. 2A, 2B, 2C, and 2D are SEM photos of a patterned resist preparedusing a polymer blend of the invention, as described in Example 12(using 193 nm exposure).

FIG. 3 is an SEM photo of an analogous patterned blend resist, alsoprepared as described in Example 12, but using a 157 nm exposure.

DETAILED DESCRIPTION OF THE INVENTION

I. Definitions and Nomenclature

Unless otherwise indicated, this invention is not limited to specificcompositions, components, or process steps. It should also be noted thatthe singular forms “a” and “the” are intended to encompass pluralreferents, unless the context clearly dictates otherwise. Theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting.

In this specification and in the claims that follow, reference will bemade to a number of terms, which shall be defined to have the followingmeanings:

As used herein, the phrase “having the formula” or “having thestructure” is not intended to be limiting and is used in the same waythat the term “comprising” is commonly used.

The term “alkyl” as used herein refers to a linear or branched,saturated hydrocarbon substituent that generally, although notnecessarily, contains 1 to about 24 carbon atoms, such as methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl,tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. Generally,although again not necessarily, alkyl groups herein contain 1 to about12 carbon atoms. The term “lower alkyl” intends an alkyl group of 1 to 6carbon atoms, and the term “cycloalkyl” intends a cyclic alkyl group,typically having 3 to 8, preferably 3 to 7, carbon atoms. The term“substituted alkyl” refers to alkyl substituted with one or moresubstituent groups, i.e., wherein a hydrogen atom is replaced with anon-hydrogen substituent group, and the terms “heteroatom-containingalkyl” and “heteroalkyl” refer to alkyl substituents in which at leastone carbon atom is replaced with a heteroatom such as O, N, or S. If nototherwise indicated, the terms “alkyl” and “lower alkyl” include linear,branched, cyclic, unsubstituted, substituted, and/orheteroatom-containing alkyl and lower alkyl, respectively.

The term “alkylene” as used herein refers to a difunctional linear orbranched saturated hydrocarbon linkage, typically although notnecessarily containing 1 to about 24 carbon atoms, such as methylene,ethylene, n-propylene, n-butylene, n-hexylene, decylene, tetradecylene,hexadecylene, and the like. Preferred alkylene linkages contain 1 toabout 12 carbon atoms, and the term “lower alkylene” refers to analkylene linkage of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms.The term “substituted alkylene” refers to an alkylene linkagesubstituted with one or more substituent groups, i.e., wherein ahydrogen atom is replaced with a non-hydrogen substituent group, and theterms “heteroatom-containing alkylene” and “heteroalkylene” refer toalkylene linkages in which at least one carbon atom is replaced with aheteroatom. If not otherwise indicated, the terms “alkylene” and “loweralkylene” include linear, branched, cyclic, unsubstituted, substituted,and/or heteroatom-containing alkylene and lower alkylene, respectively.

The term “alkoxy” as used herein refers to a group —O-alkyl wherein“alkyl” is as defined above.

The term “aryl” as used herein, and unless otherwise specified, refersto an aromatic substituent containing a single aromatic ring or multiplearomatic rings that are fused together, directly linked, or indirectlylinked (such that the different aromatic rings are bound to a commongroup such as a methylene or ethylene moiety). Preferred aryl groupscontain 5 to 24 carbon atoms and either one aromatic ring or 2 to 4fused or linked aromatic rings, e.g., phenyl, naphthyl, biphenyl, andthe like, with more preferred aryl groups containing 1 to 3 aromaticrings, and particularly preferred aryl groups containing 1 or 2 aromaticrings and 5 to 14 carbon atoms. “Substituted aryl” refers to an arylmoiety substituted with one or more substituent groups, and the terms“heteroatom-containing aryl” and “heteroaryl” refer to an aryl group inwhich at least one ring carbon atom is replaced with a heteroatom.Unless otherwise indicated, the term “aryl” includes substituted and/orheteroaryl species.

The term “arylene” as used herein refers to an aromatic linkage definedas for “aryl” substituents above, but wherein the aryl moiety isbifunctional instead of monofunctional. Unless otherwise indicated, theterm “arylene” includes substituted and/or heteroarylene species.

The term “alicyclic” is used to refer to cyclic, non-aromatic compounds,substituents and linkages, e.g., cycloalkanes and cycloalkenes,cycloalkyl and cycloalkenyl substituents, and cycloalkylene andcycloalkenylene linkages. Often, the term refers to bridged bicycliccompounds, substituents, and linkages. Preferred alicyclic moietiesherein contain 3 to about 15 carbon atoms. Unless otherwise indicated,the term “alicyclic” includes substituted and/or heteroatom-containingsuch moieties.

The term “fluorinated” refers to replacement of a hydrogen atom in amolecule or molecular segment with a fluorine atom, and includesperfluorinated moieties. The term “perfluorinated” is also used in itsconventional sense to refer to a molecule or molecular segment whereinall hydrogen atoms are replaced with fluorine atoms. Thus, a“fluorinated” methyl group encompasses —CH₂F and —CHF₂ as well as the“perfluorinated” methyl group, i.e., —CF₃ (trifluoromethyl). The term“fluoroalkyl” refers to a fluorinated alkyl group, the term“fluoroalkylene” refers to a fluorinated alkylene linkage, the term“fluoroaryl” refers to a fluorinated aryl substituent, the term“fluoroarylene” refers to a fluorinated arylene linkage, the term“fluoroalicyclic” refers to a fluorinated alicyclic moiety, and thelike.

By “substituted” as in “substituted alkyl,” “substituted aryl,” and thelike, as alluded to in some of the aforementioned definitions, is meantthat in the alkyl, aryl, or other moiety, at least one hydrogen atombound to a carbon (or other) atom is replaced with a non-hydrogensubstituent. Examples of such substituents include, without limitation,functional groups such as halide, hydroxyl, alkoxy, acyl (includingalkylcarbonyl (—CO-alkyl) and arylcarbonyl (—CO-aryl)), acyloxy(—O-acyl), alkoxycarbonyl (—(CO)—O-alkyl), aryloxycarbonyl(—(CO)—O-aryl), and silyl (e.g., trialkylsilyl), and hydrocarbylmoieties such as alkyl, aryl, aralkyl (aryl-substituted alkyl), andalkaryl (alkyl-substituted aryl). The aforementioned functional groupsmay, if a particular group permits, be further substituted with one ormore additional functional groups or with one or more hydrocarbylmoieties such as those specifically enumerated above, and analogously,the above-mentioned hydrocarbyl moieties may be further substituted withone or more functional groups or additional hydrocarbyl moieties such asthose specifically enumerated.

The term “polymer” is used to refer to a chemical compound thatcomprises linked monomers, and that may be linear, branched, orcrosslinked. The term also encompasses not only homopolymers, but alsocopolymers, terpolymers, and the like. The term “copolymer,” unlessspecifically indicated otherwise, refers to a polymer containing atleast two different monomer units.

When two substituents are indicated as being “taken together to form aring,” several possibilities are encompassed. That is, when R and R′ ofthe following hypothetical compound are indicated as being takentogether to form a ring

the resulting compounds include (1) those wherein a single spacer atomlinks the carbon atoms indicated at * and ** (i.e., R and R′ “takentogether” together form a single atom that may or may not besubstituted, e.g., CH₂ or O), (2) those wherein a direct covalent bondis formed between R and R′, and (3) those wherein R and R′ are linkedthrough a bifunctional moiety containing one or more spacer atoms, asrespectively illustrated in the following structures.

In addition, compounds in which R and R′ are “taken together to form aring” include compounds in which the linked atoms are not necessarilycontained within a terminal group. For example, when R of the aboveformula is —CH₂CH₃ and R′ is —CH₂CF₃, such that the compound has thestructure

then compounds in which R and R′ are taken together to form a ringinclude both

The term “ring” is intended to include all types of cyclic groups,although the rings of primary interest herein are alicyclic, includingcycloalkyl and substituted and/or heteroatom-containing cycloalkyl,whether monocyclic, bicyclic (including bridged bicyclic), orpolycyclic. Preferred rings are substituted and/or heteroatom-containingmonocyclic rings.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, the phrase “optionally substituted” means that anon-hydrogen substituent may or may not be present on a given atom, and,thus, the description includes structures wherein a non-hydrogensubstituent is present and structures wherein a non-hydrogen substituentis not present.

The term “acid-labile” refers to a molecular segment containing at leastone covalent bond that is cleaved upon exposure to acid.

Analogously, the term “acid-inert” refers to a substituent that is notcleaved or otherwise chemically modified upon contact withphotogenerated acid.

The terms “photogenerated acid” and “photoacid” are used interchangeablyherein to refer to the acid that is created upon exposure of the presentcompositions to radiation, i.e., as a result of the radiation-sensitiveacid generator in the compositions.

The term “substantially transparent” as used to describe a polymer thatis “substantially transparent” to radiation of a particular wavelengthrefers to a polymer that has an absorbance of less than about5.0/micron, preferably less than about 4.0/micron, most preferably lessthan about 3.5/micron, at a selected wavelength.

For additional information concerning terms used in the field oflithography and lithographic compositions, see Introduction toMicrolithography, Eds. Thompson et al. (Washington, D.C.: AmericanChemical Society, 1994).

II. The Fluorinated Vinyl Ethers and Copolymers Thereof

The fluorinated vinyl ether monomers of the invention used to preparecopolymers for incorporation into lithographic photoresists are composedof ethylene directly substituted on an olefinic carbon atom with amoiety —OR* and optionally further substituted on an olefinic carbonatom with one, two, or three additional nonhydrogen substituents,wherein R* comprises a fluorinated alkyl moiety substituted with aprotected or unprotected hydroxyl group, and further wherein an atomwithin R* may be (a) taken together with one of the additionalnonhydrogen substituents, if present, or (b) directly bound to anolefinic carbon atom, to form a ring.

In a preferred embodiment, R* has the structure -L-C(CX₃)(CY₂Z)(OR⁴),such that the fluorinated vinyl ether has the structure of formula (I)

wherein the various substituents are as follows.

The linker L is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂alkylene (e.g., C₁-C₁₂ fluoroalkylene), C₁-C₁₂ heteroalkylene,substituted C₁-C₁₂ heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅fluoroalicyclic, C₅-C₁₄ aryl, substituted C₅-C₁₄ arylene (e.g., C₅-C₁₄fluoroarylene), C₅-C₁₄ heteroarylene, and substituted C₅-C₁₄heteroarylene, or may be comprised of a combination of two or more ofthe aforementioned linkages. Preferred L moieties include, withoutlimitation, C₁-C₁₂ alkylene, C₁-C₁₂ fluoroalkylene, C₃-C₁₅ alicyclic,C₃-C₁₅ fluoroalicyclic, C₅-C₁₄ arylene, C₅-C₁₄ fluoroarylene, andcombinations thereof. In a more preferred embodiment, L is C₁-C₁₂alkylene, C₃-C₁₅ alicyclic, or a combination thereof. For example, L maybe —(CH₂)₃—, —CH₂—CH(CH₃)—CH₂—, —(CH₂)₄—, —(CH₂)₅—, norbornanyl (NB),adamantanyl (AD), —NB—CH₂—, etc.

X is H or F, and Y is H or F, providing that when X is H, then Y is F. Zis identical to Y, or is taken together with another substituent to forma ring, as described infra. In the latter case, the carbon atom to whichZ is attached—as well as Z per se—may be directly bound to eitherolefinic carbon atom in order to form a ring. Analogously, a ring may beformed when the carbon atom to which the Y substituents are attached isdirectly bound to one of the olefinic carbon atoms.

R¹ is selected from: H; C₁-C₁₂ alkyl, preferably lower alkyl;fluorinated C₁₋₁₂ alkyl; and C₃-C₁₅ alicyclic. In a particularlypreferred embodiment, R¹ is H.

R² is also selected from: H; C₁-C₁₂ alkyl, preferably lower alkyl;fluorinated C₁₋₁₂ alkyl, and C₃-C₁₅ alicyclic. R², however, may also betaken together with either L or Z to form a ring, e.g., a five-memberedto nine-membered ring, as will be described infra. In a particularlypreferred embodiment, R² is H.

R³ is selected from H, C₁-C₁₂ alkyl, and C₃-C₁₅ alicyclic, or R³ and oneof R¹, L, and Z are taken together to form a ring, e.g., a five-memberedto nine-membered ring. In a preferred embodiment, R³ is H or C₁-C₁₂alkyl, more preferably H or lower alkyl, most preferably H.

When R¹ and R³ are taken together to form a ring, R² is preferably H. Inthis case, there is a linkage between R¹ and R³ that typically containsthree to seven spacer atoms, preferably three to five spacer atoms,which is generally alkylene or substituted and/or heteroatom-containingalkylene. As an example, when R¹ and R³ are linked through anunsubstituted alkylene chain, the fluorinated vinyl ether has thestructure of formula (III)

wherein n is preferably 1, 2, 3, 4, or 5 and L, X, Y, Z, R², and R⁴ areas defined previously. When the ring formed between R¹ and R³ is five-to seven-membered, n is then 1, 2, or 3.

When R² and L are taken together to form a ring, R¹ and R³ arepreferably although not necessarily H. Generally, the ring is a five- tonine-membered ring, preferably a five- to seven-membered ring, which isgenerally a cycloalkyl ring that is optionally substituted and/orheteroatom-containing. One such group of compounds is represented by thestructure of formula (IV)

wherein X, Y, Z, and R⁴ are as defined previously, n1 and n2 areintegers in the range of zero to 5, the sum of n1 and n2 is in the rangeof 1 to 5, preferably in the range of 1 to 3, and L^(x) is a direct bondor represents a terminal segment of L extending from the carbon atomwithin L that is bound to R².

Analogously, when R³ and L are taken together to form a ring, typicallya five- to nine-membered ring, preferably a five- to seven-memberedring, which is generally a cycloalkyl ring that is optionallysubstituted and/or heteroatom-containing, then R¹ and R² are preferablyalthough not necessarily H. One group of such structures, when thelinkage is unsubstituted alkylene, is represented by formula (V)

wherein X, Y, Z, and R⁴ are as defined previously, n3 and n4 areintegers in the range of zero to 5, the sum of n3 and n4 is 1 to 5,preferably 1 to 3, and L^(x) is a direct bond or represents a terminalsegment of L extending from the carbon atom within L that is bound toR³.

When Z is taken together with R² or R³ to form a ring, which isgenerally a cycloalkyl ring that is optionally substituted and/orheteroatom-containing, however, the structures are somewhat different,insofar as the CY² moiety is then a member of the ring rather thancontained within an extending substituent. Here, R¹ and R³ arepreferably H. An example of such a compound is that represented by thestructure of formula (VI)

wherein X, Y, and R⁴ are as defined previously, n5 is zero, 1, 2, or 3,n6 is 1, 2, or 3, and the sum of n5 and n6 is generally 1, 2, 3, 4, or5, more typically 1 or 2. In a variation on this compound, a cyclicfluorinated vinyl ether of the invention may also have the structure offormula (VIA)

Similarly, when R³ is taken together with Z to form a ring, which isgenerally a cycloalkyl ring that is optionally substituted and/orheteroatom-containing, R¹ and R² are preferably H. Such a compound maybe represented by the structure of formula (VII)

wherein n7 is zero, 1, 2, or 3, n8 is 1, 2, or 3, and the sum of n5 andn6 is generally 1, 2, 3, 4, or 5, preferably 2, 3, or 4. In a variationon this compound, a cyclic fluorinated vinyl ether of the invention mayalso have the structure of formula (VIIA)

In all of these molecular structures, i.e., (I) and (III) through (VII),R⁴ is selected from H, an acid-labile group optionally substituted withone or more fluorine atoms, and an acid-inert moiety optionallysubstituted with one or more fluorine atoms.

Acid-inert R⁴ moieties include, by way of example, fluorinated alkylgroups, with fluorinated lower alkyl groups preferred, and fluorinatedalkanol groups, including fluorinated lower alkanol groups. Examples offluorinated lower alkanol groups are -L-C(CX₃)(CY₂Z)-OH, wherein L, X,Y, and Z are as defined previously. Acid-inert moieties also includealkyl and cycloalkyl groups that do not contain a tertiary attachmentpoint.

Acid-labile R⁴ moieties include tertiary alkyl, e.g., t-butyl, or acyclic or alicyclic substituent (generally C₆-C₁₂) with a tertiaryattachment point such as adamantyl, norbornyl, isobornyl,2-methyl-2-adamantyl, 2-methyl-2-isobornyl,2-methyl-2-tetracyclododecenyl,2-methyl-2-dihydrodicyclo-pentadienyl-cyclohexyl, 1-methylcyclohexyl, or1-methylcyclopentyl (MCP). Acid-labile moieties also include-(Q-CO—O)_(x)—R¹⁴, -(Q)_(y)—(CO)—O—R¹⁵, —CR¹⁶R¹⁷—O—R¹⁸, andtrialkylsilyl (preferably tri(lower alkyl)silyl), wherein x and y areintegers, typically in the range of 1 to 8 inclusive, Q is an alkylenegroup optionally substituted with one or more fluorine atoms, y is zero(i.e., Q is not present) or 1, R¹⁴ and R¹⁵ are optionally substitutedhydrocarbyl, typically alkyl or fluorinated alkyl, preferably loweralkyl or fluorinated lower alkyl, R¹⁶ and R¹⁷ are H, alkyl (typicallylower alkyl), fluoroalkyl (typically lower fluoroalkyl), or alicyclic,or are taken together to form a ring, typically a five- toseven-membered ring, and R¹⁸ is alkyl (typically lower alkyl),fluoroalkyl (typically lower fluoroalkyl), or alicyclic, or can be takentogether with R¹⁶ or R¹⁷ to form a ring, e.g., a five- to nine-membered,preferably a five- to seven-membered heterocyclic ring that may or maynot contain an additional heteroatom.

Other examples of acid-labile groups are set forth in U.S. Pat. No.4,491,628 to Ito et al., entitled “Positive- and Negative-Working ResistCompositions with Acid-Generating Photoinitiator and Polymer with AcidLabile Groups Pendant from Polymer Backbone,” and in the Handbook ofMicrolithography, Micromachining, and Microfabrication, Vol. 1:Microlithography, Ed. P. Raj-Coudhury, p. 321 (1997). Still othersuitable acid-labile groups may be found in U.S. Pat. No. 5,679,495 toYamachika et al. or in the pertinent literature and texts (e.g., Greeneet al., Protective Groups in Organic Synthesis, 2^(nd) Ed. (New York:John Wiley & Sons, 1991)).

Exemplary and particularly preferred fluorinated vinyl ethers of formula(I) are VE-PrHFA(1,1,1-trifluoro-2-trifluoromethyl-5-vinyloxy-pentan-2-ol) and VE-NBHFA(1,1,1,3,3,3-hexafluoro-(6- or5-)vinyloxy-bicyclo[2.2.1]hept-2-ylmethyl)-propan-2-ol):

Synthesis of these fluorinated vinyl ethers is described in Examples 1,2, 3, and 4.

Fluorinated vinyl ethers of the invention may be synthesized from astarting material having the structure of formula (VIII) or (VIIIA)

wherein Q is a segment of L, i.e., L is —CH₂CH₂-Q- in formula (VIII),and is —CH₂-Q- in formula (VIIIA). These alcohols may be derived fromhydration of the corresponding olefin (IX)

To convert (VIII) or (VIIIA) to a fluorinated vinyl ether of theinvention, the compound is transetherified with an appropriatelysubstituted co-reactant in the presence of an Hg or Ir catalyst (seeWatanabe et al. (1957) J. Am. Chem. Soc. 79:2828 and Okimoto et al.(2002) J. Am. Chem. Soc. 124:1590). With an Hg catalyst, e.g., Hg(OAc)₂(Ac=acetyl), the co-reactant is CR¹R²═CR³(OR¹⁹) wherein R¹, R², and R³are as defined previously, and R¹⁹ is lower alkyl, e.g., ethyl. With anIr catalyst, e.g., [Ir(COD)Cl]₂ (COD=cyclooctadiene), the co-reactant isCR¹R²═CR³(OR²⁰) wherein R¹, R², and R³ are as defined previously, andR²⁰ is lower acyl, e.g., acetyl. See Examples 1 through 5. A significantadvantage of these syntheses is that the desired product can besynthesized directly from the corresponding diol, i.e., compound (VIII)wherein R⁴ is H, without having to protect the acidic fluoroalcohol(—C(CX₃)(CY₂Z)-OH) moiety. Of course, other syntheses may also be usedto prepare the fluorinated vinyl ethers of the invention, includingsyntheses that are known or may become known to those of ordinary skillin the art, and/or syntheses that are described in the pertinent textsand literature references.

In another embodiment, a fluorinated copolymer is prepared bycopolymerization of at least one fluorinated vinyl ether of theinvention, preferably having the structure of formula (I), and at leastone monomer having the structure of formula (II)

wherein the substituents are as follows:

R⁵ is selected from F, lower fluoroalkyl, cyano, —(CO)—O—R⁹,—(CO)—NR¹⁰R¹¹,

—(CO)—R¹², and —S(O)₂—OR¹³, or is taken together with R⁶ or R⁸ to form aring, generally a five- to nine-membered ring. Preferably, R⁵ isselected from F, lower fluoroalkyl, and cyano, and more preferably is F,lower fluoroalkyl (e.g., trifluoromethyl) or cyano.

R⁶, R⁷, and R⁸ are independently selected from H, F, lower alkyl, lowerfluoroalkyl, cyano, —(CO)—O—R⁹, —(CO)—NR¹⁰R¹¹, —(CO)—R¹², and—S(O)₂—OR¹³, and, in addition, R⁷ may be taken together with R⁶ or R⁸ toform a ring, generally a five- to nine-membered ring, typically a five-to seven-membered ring. In the latter case, when R⁷ is taken togetherwith R⁶ or R⁸ to form a ring, the ring is preferably formed through analkylene linkage that is optionally substituted and/orheteroatom-containing, thus including, for example, lactones and cyclicanhydrides. Monomers containing such rings include, without limitation,maleic anhydride, itaconic anhydride, and α-methylene-γ-butyrolactone.

In the foregoing substituents, R⁹ is H, an acid-labile moiety optionallysubstituted with one or more fluorine atoms, or an acid-inert moietyoptionally substituted with one or more fluorine atoms, and R¹⁰, R¹¹,R¹², and R¹³ are independently selected from H, C₁-C₁₂ alkyl,substituted C₁-C₁₂ alkyl, C₁-C₁₂ heteroalkyl, substituted C₁-C₁₂heteroalkyl, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, C₅-C₁₄ aryl,substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl, and substituted C₅-C₁₄heteroarylene. In a preferred embodiment, R⁶ and R⁷ substituents areboth H when R⁵ is lower fluoroalkyl or cyano, and are both F when R⁵ isF. In the aforementioned preferred embodiment, R⁸ is preferably selectedfrom F, cyano, and —(CO)—O—R⁹, in which R⁹ is as defined above, withpreferred R⁹ groups selected from acid-labile substituents optionallysubstituted with a moiety -L-C(CX₃)(CY₂Z)-OH. Most preferably, R⁹ is anacid-labile moiety selected from tertiary alkyl substituents and C₆-C₁₂alicyclic substituents with a tertiary attachment point.

Accordingly, in a preferred embodiment, the co-monomer has the structureof formula (X)

wherein R⁵ is F, trifluoromethyl, or cyano, and R⁹ is H, an acid-labilegroup such as t-butyl or 1-methylcyclopentyl, or is a “fluoroalcohol”substituent such as -L-C(CX₃)(CY₂Z)-OH, e.g., hexafluoroisopropanol(—C(CF₃)₂—OH). In many preferred compounds, R⁶ and R⁷ are both H when R⁵is lower fluoroalkyl or cyano, and are both F when R⁵ is F.

Examples of structure (II) monomers that are preferred include, but arenot limited to, the following:

The above abbreviations are as follows:TBTFMA=t-butyl-2-trifluoromethylacrylate;TFMA=α-trifluoromethylacrylate;NBHFA=5-[(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]-2-(or-3-)norbornane; and TFMAN=α-trifluoromethyl acrylonitrile. Othersuitable monomers are described in U.S. Pat. No. 6,509,134 to Ito etal., U.S. Patent Publication No. 2002/0102490 to Brock et al., and U.S.Patent Publication No. 2002/0146639 to Brock et al., all assigned toInternational Business Machines Corporation.

It will also be appreciated that structure (II) comonomers includestructurally simple fluorine-containing acid-inert monomers such asCF₂═CF₂, (CF₃)₂C═CF₂, (CF₃)₂C═C(CF₃)₂, (CF₃)CH═CH(CF₃), andα-trifluoromethylstyrene (TFMST).

The copolymer may be prepared from one or more monomers having thestructure of formula (I) and from one or more monomers having thestructure of formula (II). For example, the copolymer may be preparedfrom two monomers having the structure of formula (I) and two monomershaving the structure of formula (II). Furthermore, the copolymer mayalso be prepared by using one or more additional monomers not having thestructure of formula (I) or formula (II). These monomers will also beaddition polymerizable monomers, preferably radically copolymerizablevinyl monomers, and may be advantageously substituted with groups thatlower absorbance at 157 nm.

These additional monomers that can be copolymerized along with structure(I) and structure (II) monomers include, without limitation, acrylicacid, methacrylic acid, or trifluoromethacrylic acid, which may beadvantageously incorporated to enhance the development and adhesionproperties of the resist. The copolymer may also comprise other suitablemonomer units such as hydroxystyrene to enhance development and etchresistance, or a silicon-containing monomer unit (e.g., asilicon-containing acrylate, methacrylate or styrene) to enhance oxygenplasma etch resistance for bilayer applications. The additional monomersalso include vinyl sulfonates and maleic anhydride. In general, suitablecomonomers to be used in addition to those of formulae (I) and (II)include, but are not limited to, the following ethylenically unsaturatedpolymerizable monomers: acrylic and methacrylic acid esters and amides,including alkyl acrylates, aryl acrylates, alkyl methacrylates and arylmethacrylates (for example, methyl acrylate, methyl methacrylate,n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butylmethacrylate, 2-ethylhexyl methacrylate, benzyl acrylate andN-phenylacrylamide); vinyl aromatics, including unsubstituted styreneand styrene substituted with one or two lower alkyl, halogen or hydroxylgroups (for example, styrene derivatives such as 4-vinyltoluene,4-vinylphenol, α-methylstyrene, 2,5-dimethylstyrene, 4-t-butylstyreneand 2-chlorostyrene); butadiene; vinyl acetate; vinyl bromide;vinylidene chloride; fluorinated analogs of any of the foregoing, e.g.,fluorinated acrylic and methacrylic acid esters (e.g., fluorinated alkylacrylates, fluorinated aryl acrylates, fluorinated alkyl methacrylatesand fluorinated aryl methacrylates); vinyl sulfonates, maleic anhydride;and others readily apparent to one skilled in the art.

The copolymer formed from structures (I) and (II) above is comprised ofmonomer units having the structure (XI)

and monomer units having the structure (XII)

where L, X, Y, Z, and R¹ through R⁸ are as defined previously. Thecopolymer may also include one or more additional monomer units derivingfrom the incorporation of additional monomers into the polymerizationreaction as described above.

The copolymer may advantageously have molar fractions of the monomerunits (XI) and (XII) in the range of approximately 0.1 to 0.9 and 0.9 to0.1, respectively, with the molar fraction of the additional monomerunit(s) in the range of zero to approximately 0.5.

The copolymers provided herein can be prepared by radicalcopolymerization, using a suitable free radical initiator. The initiatormay be any conventional free radical-generating polymerizationinitiator. Examples of suitable initiators include peroxides such asO-t-amyl-O-(2-ethylhexyl)monoperoxycarbonate, dipropylperoxydicarbonate,and benzoyl peroxide (BPO), as well as azo compounds such asazobisisobutyronitrile (AIBN),2,2′-azobis(2-amidino-propane)dihydrochloride, and2,2′-azobis(isobutyramide)dihydrate. The initiator is generally presentin the polymerization mixture in an amount of from about 0.2 to 5% byweight of the monomers. The resulting copolymer typically has a numberaverage molecular weight in the range of approximately 500 to 50,000,generally in the range of approximately 1,000 to 20,000.

III. Resist Compositions

In another embodiment, a photoresist composition is provided thatcomprises both a copolymer as described in detail above and a photoacidgenerator, with the copolymer representing up to about 99 wt. % of thesolids included in the composition, and the photoacid generatorrepresenting approximately 0.5 to 10 wt. % of the solids contained inthe composition. Other components and additives (e.g., dissolutionmodifying additives such as dissolution inhibitors) may also be present.For improved transparency at 157 nm, the dissolution modifying additiveis preferably a fluorine-containing material.

The copolymer may be incorporated into the resist composition as is, orin the form of a blend with one or more additional polymers. Any suchadditional polymers are generally selected to increase transparency at adesired wavelength, e.g., 157 nm or 193 nm, increase dry etchresistance, and/or improve aqueous base development. Additional polymersinclude, by way of example, norbornene polymers. A preferred group ofsuch polymers are those described in U.S. Ser. No. 10/090,646, citedearlier herein, which are comprised of monomer units having thestructure of formula (XIII)

wherein: q is zero or 1; r is zero or 1; Ln is a linking group and isdefined as for L; R²¹ is defined as for X; R²² is defined as for Y; andR²³ is defined as for R⁴. The polymer may be a homopolymer, as inPNBHFA, or it may be a copolymer containing additional types of monomerunits, e.g., resulting from polymerization of monomers of formula (II)or other norbornene monomers.

The photoacid generator may be any compound that, upon exposure toradiation, generates a strong acid and is compatible with the othercomponents of the photoresist composition. Examples of preferredphotochemical acid generators (PAGs) include, but are not limited to,α-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT), onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts and sulfonic acid esters of N-hydroxyamides orN-hydroxyimides, as disclosed in U.S. Pat. No. 4,731,605. Also, a PAGthat produces a weaker acid such as the dodecane sulfonate ofN-hydroxy-naphthalimide (DDSN) may be used. Combinations of PAGs may beused. Generally, suitable acid generators have high thermal stability(are preferably stable to temperatures greater than 140° C.) so they arenot degraded during pre-exposure processing. In addition to MDT andDDSN, suitable sulfonate compounds are sulfonate salts, but othersuitable sulfonate PAGs include sulfonated esters and sulfonyloxyketones. See U.S. Pat. No. 5,344,742 to Sinta et al., and J.Photopolymer Science and Technology, 4:337 (1991), for disclosure ofsuitable sulfonate PAGs, including benzoin tosylate,t-butylpheny-α-(p-toluenesulfonyloxy)acetate andt-butyl-α-(p-toluenesulfonyloxy)-acetate. Onium salts are also generallypreferred acid generators of compositions provided herein. Onium saltsthat contain weakly nucleophilic anions have been found to beparticularly suitable. Examples of such anions are the halogen complexanions of divalent to heptavalent metals or non-metals, for example, Sb,B, P, and As. Examples of suitable onium salts are aryl-diazonium salts,halonium salts, aromatic sulfonium salts and sulfoxonium salts orselenium salts, (e.g., triarylsulfonium and diaryliodoniumhexafluoroantimonates, hexafluoroarsenates, trifluoromethanesulfonatesand others). One preferred diaryliodonium salt is iodoniumperfluorooctanesulfonate and is disclosed in U.S. Pat. No. 6,165,673 toBreyta et al. Examples of suitable preferred onium salts can be found inU.S. Pat. Nos. 4,442,197, 4,603,101, and 4,624,912. Other useful acidgenerators include the family of nitrobenzyl esters, and the s-triazinederivatives. Suitable s-triazine acid generators are disclosed, forexample, in U.S. Pat. No. 4,189,323.

Still other suitable acid generators include: sulfonyloxynaphthalimidessuch as N-camphorsulfonyloxynaphthalimide andN-pentafluorophenylsulfonyloxynaphthalimide; ionic iodonium sulfonates,e.g., diaryl iodonium (alkyl or aryl) sulfonate andbis-(di-t-butylphenyl)-iodonium camphanylsulfonate;perfluoroalkanesulfonates, such as perfluoropentanesulfonate,perfluorooctanesulfonate, and perfluoromethanesulfonate; aryl (e.g.,phenyl or benzyl)triflates and derivatives and analogs thereof, e.g.,triphenylsulfonium triflate or bis-(t-butylphenyl)iodonium triflate;pyrogallol derivatives (e.g., trimesylate of pyrogallol);trifluoromethanesulfonate esters of hydroxyimides; α,α′-bis-sulfonyl-diazomethanes; sulfonate esters of nitro-substitutedbenzyl alcohols; naphthoquinone-4-diazides; and alkyl disulfones. Othersuitable photoacid generators are disclosed in Reichmanis et al. (1991),Chemistry of Materials 3:395, and in U.S. Pat. No. 5,679,495 toYamachika et al. Additional suitable acid generators useful inconjunction with the compositions and methods provided herein will beknown to those skilled in the art and/or are described in the pertinentliterature.

With a positive photoresist composition, a dissolution modifyingadditive, generally although not necessarily a dissolution inhibitor, isincluded, while with a negative photoresist composition, a crosslinkingagent will be present. If dissolution inhibitors and crosslinking agentsare present, they will typically represent in the range of about 1 wt. %to 40 wt. %, preferably about 5 wt. % to 30 wt. %, of the total solids.

Suitable dissolution inhibitors will be known to those skilled in theart and/or described in the pertinent literature. Preferred dissolutioninhibitors have high solubility in the resist composition and thesolvent used to prepare solutions of the resist composition (e.g.,propylene glycol methyl ether acetate, or “PGMEA”), exhibit strongdissolution inhibition, have a high exposed dissolution rate, aresubstantially transparent at the wavelength of interest, may exhibit amoderating influence on T_(g), strong etch resistance, and display goodthermal stability (i.e., stability at temperatures of about 140° C. orgreater). Suitable dissolution inhibitors include, but are not limitedto, bisphenol A derivatives, e.g., wherein one or both hydroxyl moietiesare converted to a t-butoxy substituent or a derivative thereof such asa t-butoxycarbonyl or t-butoxycarbonylmethyl group; fluorinatedbisphenol A derivatives such as CF₃-bisphenol A-OCH₂(CO)—O-tBu(6F-bisphenol A protected with a t-butoxycarbonylmethyl group); normalor branched chain acetal groups such as 1-ethoxyethyl, 1-propoxyethyl,1-n-butoxyethyl, 1-isobutoxy-ethyl, 1-t-butyloxyethyl, and1-t-amyloxyethyl groups; and cyclic acetal groups such astetrahydrofuranyl, tetrahydropyranyl, and 2-methoxytetrahydro-pyranylgroups; androstane-17-alkylcarboxylates and analogs thereof, wherein the17-alkylcarboxylate at the 17-position is typically lower alkyl.Examples of such compounds include lower alkyl esters of cholic,ursocholic and lithocholic acid, including methyl cholate, methyllithocholate, methyl ursocholate, t-butyl cholate, t-butyl lithocholate,t-butyl ursocholate, and the like (see, e.g., Allen et al. (1995) J.Photopolym. Sci. Technol., cited supra); hydroxyl-substituted analogs ofsuch compounds (ibid.); and androstane-17-alkylcarboxylates substitutedwith 1 to 3 C₁-C₄ fluoroalkyl carbonyloxy substituents, such as t-butyltrifluoroacetyllithocholate (see, e.g., U.S. Pat. No. 5,580,694 to Allenet al.).

Preferred dissolution inhibitors herein are fluoroalcohol-baseddissolution inhibitors such as those having the structure (XIV)

wherein R²⁴ and R²⁵ are acid-labile groups such as -(Q′—CO—O)_(x1)—R²⁶,-(Q′)_(y1)—(CO)—O—R²⁷, and —CR²⁸R²⁹—O—R³⁰ wherein R²⁶, R²⁷, R²⁸, R²⁹,and R³⁰ are defined as for R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸, respectively, x1and y1 are integers in the range of 1 to 8 inclusive, and Q′ is definedas for Q.

The crosslinking agent used in the photoresist compositions providedherein may be any suitable crosslinking agent known in the negativephotoresist art which is otherwise compatible with the other selectedcomponents of the photoresist composition. The crosslinking agentspreferably act to crosslink the polymer component in the presence of agenerated acid. Preferred crosslinking agents are glycoluril compoundssuch as tetramethoxymethyl glycoluril, methylpropyltetramethoxymethylglycoluril, and methylphenyltetramethoxymethyl glycoluril, availableunder the POWDERLINK trademark. from American Cyanamid Company. Otherpossible crosslinking agents include 2,6-bis(hydroxymethyl)-p-cresol andanalogs and derivatives thereof, such as those found in JapaneseLaid-Open Patent Application (Kokai) No. 1-293339, as well as etherifiedamino resins, for example methylated or butylated melamine resins(N-methoxymethyl- or N-butoxymethyl-melamine respectively) ormethylated/butylated glycolurils, for example as can be found inCanadian Patent No. 1 204 547. Combinations of crosslinking agents maybe used.

The remainder of the resist composition is composed of a solvent and mayadditionally, if necessary or desirable, include customary additivessuch as dyes, sensitizers, additives used as stabilizers andacid-diffusion controlling agents, coating aids such as surfactants oranti-foaming agents, adhesion promoters and plasticizers.

The choice of solvent is governed by many factors not limited to thesolubility and miscibility of resist components, the coating process,and safety and environmental regulations. Additionally, inertness toother resist components is desirable. It is also desirable that thesolvent possess the appropriate volatility to allow uniform coating offilms yet also allow significant reduction or complete removal ofresidual solvent during the post-application bake process. See, e.g.,Introduction to Microlithography, Eds. Thompson et al., citedpreviously. In addition to the above components, the photoresistcompositions provided herein generally include a casting solvent todissolve the other components so that the overall composition may beapplied evenly on the substrate surface to provide a defect-freecoating. Where the photoresist composition is used in a multilayerimaging process, the solvent used in the imaging layer photoresist ispreferably not a solvent to the underlayer materials, otherwise theunwanted intermixing may occur. The invention is not limited toselection of any particular solvent. Suitable casting solvents maygenerally be chosen from ether-, ester-, hydroxyl-, andketone-containing compounds, or mixtures of these compounds. Examples ofappropriate solvents include carbon dioxide, cyclopentanone,cyclohexanone, ethyl 3-ethoxypropionate (EEP), a combination of EEP andγ-butyrolactone (GBL), lactate esters such as ethyl lactate, alkyleneglycol alkyl ether esters such as PGMEA, alkylene glycol monoalkylesters such as methyl cellosolve, butyl acetate, and 2-ethoxyethanol.Preferred solvents include ethyl lactate, propylene glycol methyl etheracetate, ethyl 3-ethoxypropionate and their mixtures. The above list ofsolvents is for illustrative purposes only and should not be viewed asbeing comprehensive nor should the choice of solvent be viewed aslimiting the invention in any way. Those skilled in the art willrecognize that any number of solvents or solvent mixtures may be used.

Greater than 50 percent of the total mass of the resist formulation istypically composed of the solvent, preferably greater than 80 percent.

Other customary additives include dyes that may be used to adjust theoptical density of the formulated resist and sensitizers which enhancethe activity of photoacid generators by absorbing radiation andtransferring it to the photoacid generator. Examples include aromaticssuch as functionalized benzenes, pyridines, pyrimidines, biphenylenes,indenes, naphthalenes, anthracenes, coumarins, anthraquinones, otheraromatic ketones, and derivatives and analogs of any of the foregoing.

A wide variety of compounds with varying basicity may be used asstabilizers and acid-diffusion controlling additives. They may includenitrogenous compounds such as aliphatic primary, secondary, and tertiaryamines, cyclic amines such as piperidines, pyrimidines, morpholines,aromatic heterocycles such as pyridines, pyrimidines, purines, iminessuch as diazabicycloundecene, guanidines, imides, amides, and others.Ammonium salts may also be used, including ammonium, primary, secondary,tertiary, and quaternary alkyl- and arylammonium salts of alkoxidesincluding hydroxide, phenolates, carboxylates, aryl and alkylsulfonates, sulfonamides, and others. Other cationic nitrogenouscompounds including pyridinium salts and salts of other heterocyclicnitrogenous compounds with anions such as alkoxides including hydroxide,phenolates, carboxylates, aryl and alkyl sulfonates, sulfonamides, andthe like may also be employed. Surfactants may be used to improvecoating uniformity, and include a wide variety of ionic and non-ionic,monomeric, oligomeric, and polymeric species. Likewise, a wide varietyof anti-foaming agents may be employed to suppress coating defects.Adhesion promoters may be used as well; again, a wide variety ofcompounds may be employed to serve this function. A wide variety ofmonomeric, oligomeric, and polymeric plasticizers such as oligo- andpolyethyleneglycol ethers, cycloaliphatic esters, and non-acid reactivesteroidally derived materials may be used as plasticizers, if desired.However, neither the classes of compounds nor the specific compoundsmentioned above are intended to be comprehensive and/or limiting. Oneversed in the art will recognize the wide spectrum of commerciallyavailable products that may be used to carry out the types of functionsthat these customary additives perform.

Typically, the sum of all customary additives will comprise less than 20percent of the solids included in the resist formulation, preferably,less than 5 percent.

IV. Use in Generation of Resist Images on a Substrate

The present invention also relates to a process for generating a resistimage on a substrate comprising the steps of: (a) coating a substratewith a film comprising a resist composition provided herein; (b)imagewise exposing the film to radiation; and (c) developing the image.The first step involves coating the substrate with a film comprising theresist composition dissolved in a suitable solvent. Suitable substratesare ceramic, metallic or semiconductive, and preferred substrates aresilicon-containing, including, for example, silicon dioxide, siliconnitride, and silicon oxynitride. The substrate may or may not be coatedwith an organic anti-reflective layer prior to deposition of the resistcomposition. Alternatively, a bilayer resist may be employed wherein aresist composition provided herein forms an upper resist layer (i.e.,the imaging layer), and the underlayer is comprised of a material thatis highly absorbing at the imaging wavelength and compatible with theimaging layer. Conventional underlayers include diazonaphthoquinone(DNQ)/novolak resist material.

Preferably, the surface of the substrate is cleaned by standardprocedures before the film is deposited thereon. Suitable solvents forthe composition are as described in the preceding section, and include,for example, cyclohexanone, ethyl lactate, and propylene glycol methylether acetate. The film can be coated on the substrate using art-knowntechniques such as spin or spray coating, or doctor blading. Preferably,before the film has been exposed to radiation, the film is heated to anelevated temperature of about 90-150∀ C. for a short period of time,typically on the order of about 1 minute. The dried film has a thicknessof about 0.02 to 5.0 microns, preferably about 0.05 to 2.5 microns, andmost preferably about 0.10 to 1.0 microns. The radiation may beultraviolet, electron beam or x-ray. Ultraviolet radiation is preferred,particularly deep ultraviolet radiation having a wavelength of less thanabout 250 nm, e.g., 157 nm using an F₂ excimer laser. The radiation isabsorbed by the radiation-sensitive acid generator to generate freeacid, which with heating (generally to a temperature of about 90-150° C.for a short period of time, on the order of about 1 minute) causescleavage of the acid-labile pendant groups and formation of thecorresponding acid. It will be appreciated by those skilled in the artthat the aforementioned description applies to a positive resist, andwith a negative resist the exposed regions would typically becrosslinked by acid.

The third step involves development of the image with a suitablesolvent. Suitable solvents include an aqueous base, preferably anaqueous base without metal ions such as the industry standard developertetramethylammonium hydroxide or choline. Other solvents may includeorganic solvents or carbon dioxide (in the liquid or supercriticalstate), as disclosed in U.S. Pat. No. 6,665,527 to Allen et al. Becausethe copolymer of the resist composition is substantially transparent at157 nm, the resist composition is uniquely suitable for use at thatwavelength. However, the resist may also be used with wavelengths of 193nm, 248 nm, or with EUV (e.g., at 13 nm) electron beam or x-rayradiation.

The pattern from the resist structure may then be transferred to thematerial of the underlying substrate. Typically, the transfer isachieved by reactive ion etching or some other etching technique. Thus,the compositions provided herein and resulting resist structures can beused to create patterned material layer structures such as metal wiringlines, holes for contacts or vias, insulation sections (e.g., damascenetrenches or shallow trench isolation), trenches for capacitorstructures, etc. as might be used in the design of integrated circuitdevices. Accordingly, the processes for making these features involves,after development with a suitable developer as above, etching thelayer(s) underlying the resist layer at spaces in the pattern whereby apatterned material layer or substrate section is formed, and removingany remaining resist from the substrate. In some instances, a hard maskmay be used below the resist layer to facilitate transfer of the patternto a further underlying material layer or section. In the manufacture ofintegrated circuits, circuit patterns can be formed in the exposed areasafter resist development by coating the substrate with a conductivematerial, e.g., a metallic material, using known techniques such asevaporation, sputtering, plating, chemical vapor deposition, orlaser-induced deposition. Dielectric materials may also be deposited bysimilar means during the process of making circuits. Inorganic ions suchas boron, phosphorous, or arsenic can be implanted in the substrate inthe process for making p-doped or n-doped circuit transistors. Examplesof such processes are disclosed in U.S. Pat. Nos. 4,855,017, 5,362,663,5,429,710, 5,562,801, 5,618,751, 5,744,376, 5,801,094, and 5,821,469.Other examples of pattern transfer processes are described in Chapters12 and 13 of Moreau, Semiconductor Lithography, Principles, Practices,and Materials (Plenum Press, 1988). It should be understood that theinvention is not limited to any specific lithographic technique ordevice structure.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof, that theforegoing description as well as the examples that follow are intendedto illustrate and not limit the scope of the invention. Other aspects,advantages and modifications within the scope of the invention will beapparent to those skilled in the art to which the invention pertains.

All patents, patent applications, and publications mentioned herein arehereby incorporated by reference in their entireties.

Experimental:

¹H and ¹³C NMR spectra were obtained at room temperature on an Avance400 spectrometer. Quantitative ¹³C NMR was run at room temperature inacetone-d₆ in an inverse-gated ¹H-decoupled mode using Cr(acac)₃ as arelaxation agent on an Avance 400 spectrometer. For polymer compositionanalysis ¹⁹F NMR (379 MHz) spectra were also obtained using a BrukerAvance 400 spectrometer. Thermo-gravimetric analysis (TGA) was performedat a heating rate of 5° C./min in N₂ on a TA Instrument Hi-Res TGA 2950Thermogravimetric Analyzer. Differential scanning calorimetry (DSC) wasperformed at a heating rate of 10° C./min on a TA Instruments DSC 2920modulated differential scanning calorimeter. Molecular weights of thepolymers were measured in tetrahydrofuran (THF) on a Waters Model 150chromatograph relative to polystyrene standards. IR spectra wererecorded on a Nicolet 510 FT-IR spectrometer on a film cast on a KBrplate. UV measurements at 157 nm were performed using a Varian CaryModel 400 spectrometer on multiple thickness on CaF₂ discs. Filmthickness was measured on a Tencor alpha-step 2000. A quartz crystalmicrobalance (QCM) was used to study the dissolution kinetics of thecopolymer films in an aqueous tetramethylammonium hydroxide (TMAH)solution (CD-26). Contact angles were measured on an AST Products VCA2500XE video contact angle system using 2 μL of filtered deionizedwater.

Unless otherwise indicated, all reagents were obtained commercially orsynthesized according to known methods. TBTFMA, TFMAN, and TFMA-NBHFAwere synthesized as described in U.S. Pat. No. 6,509,134 to Ito et al.,U.S. Patent Publication No. 2002/0102490 to Brock et al., and U.S.Patent Publication No. 2002/0146639 to Brock et al., all assigned toInternational Business Machines Corporation.

EXAMPLE 1 Synthesis of1,1,1-trifluoro-2-trifluoromethyl-5-vinyloxy-pentan-2-ol (VE-PrHFA)

(a) Preparation of 1,1,1-trifluoro-2-trifluoromethyl-2,5-pentanediol and1,1,1-trifluoro-2 -trifluoromethyl-2,4-pentanediol: To a 3-necked, 3-Lround bottomed flask equipped with an overhead stirrer, digitalthermometer and a 1-L constant-pressure addition funnel with a nitrogeninlet was added 974 mL (1.95 mol) of borane-dimethylsulfide complex (2.0M in tetrahydrofuran). The addition funnel was charged with a solutionof 353 g (1.7 mol) of 1,1,1-trifluoro-2-trifluoromethyl-4-penten-2-ol in400 mL of anhydrous tetrahydrofuran. The flask was cooled and the olefinwas added slowly with stirring while maintaining a temperature below 15°C. The mixture was stirred at room temperature for two days after whichtime it was recooled and 750 mL (2.25 mol) of 3M NaOH was addedcarefully. The reaction mixture was reduced in volume on a rotaryevaporator and subsequently co-evaporated with two 500 mL portions ofdiethyl ether. The resulting heavy oil was taken up in 300 mL of THF andthe solution transferred to a 1-L 3-necked round-bottomed flask equippedwith a 250-mL addition funnel, a digital thermometer and a magnetic stirbar. The addition funnel was charged with 250 mL of 30% hydrogenperoxide. The flask was cooled and the hydrogen peroxide added slowlywith stirring. After stirring overnight at room temperature, thesolution was diluted with 1 L of diethyl ether and adjusted to pH 6 (wetlitmus) with 5% HCl. The ether layer was separated and the aqueous layerwas extracted with 2×500 mL of ether. The combined organic phases werewashed with 2×500 mL of saturated ammonium chloride and brine, driedover MgSO₄ and evaporated to a crude yield of 379 g of a 45:55 (2°:1°)mixture of the two diols. The diols were separated by distillationthrough a 12″ Vigreux, bp 47° C. at 1.0 mm Hg (2° alcohol) and bp 55° C.at 1.0 mm Hg (1° alcohol). The 1° alcohol is a viscous oil while the 2°alcohol is a low melting solid.

(b) Synthesis of1,1,1-trifluoro-2-trifluoromethyl-5-vinyloxy-pentan-2-ol (VE-PrHFA) withchloro-1,5-cyclooctadiene iridium(I) dimer (Scheme 1)

1,1,1-Trifluoro-2-trifluoromethyl-2,5-pentanediol (11.3 g, 50 mmol),toluene (50 mL), sodium carbonate (10.6 g, 100 mmol),chloro-1,5-cyclooctadiene iridium(I) dimer (0.34 g, 0.5 mmol), vinylacetate(14 mL, 150 mmol) were placed in a dry 250 mL round-bottom flaskequipped with a stir bar, condenser, and nitrogen inlet. The reactionmixture was heated to 100° C. and stirred for 3 hours, after which timeit was cooled to room temperature. Diethyl ether (50 mL) was added toquench the reaction. After adding charcoal, the mixture was stirred for1 hr and filtered with Celite 521. Diethyl ether, excess vinyl acetate,and solvent were distilled off under reduced pressure. The degree of thetransetherification of the primary diol was found to be 52% by GC.Vacuum distillation (68-70° C., 15 mm Hg) afforded 3.13 g (25%) ofcolorless liquid.

EXAMPLE 2 Alternative Synthesis of VE-PrHFA Using Mercuric Acetate

To a 500-mL, 3-necked round bottomed flask equipped with a nitrogeninlet, digital thermometer and magnetic stir bar was added 45 g (0.2mol) of 1,1,1-trifluoro-2-trifluoromethyl-2,5-pentanediol (prepared inpart (a) of Example 1), 300 g (4.2 mol) of ethyl vinyl ether and 2.5 g(0.008 mol) of mercuric acetate and the solution stirred at roomtemperature for 2 days. The mixture was evaporated on a rotaryevaporator, diluted with 500 mL of diethyl ether and washed sequentiallywith saturated sodium bicarbonate, water and brine. After stirring overanhydrous magnesium sulfate overnight, the suspension was filtered, thesolvent removed on a rotary evaporator and the resulting oil filteredthrough a plug of silica gel as a hexane solution. Hexane was evaporatedand the resulting oil distilled four times at 70° C. @ 15 mmHg. The bestfractions were pooled to yield 17.5 g (35%) of the product as a clear,colorless oil.

EXAMPLE 3 Synthesis of 1,1,1,3,3,3-Hexafluoro-(6- or5-)vinyloxy-bicyclo[2.2.1]hept-2-ylmethyl)-propan-2-ol (VE-NBHFA)

(a) Preparation of2-hydroxy-5-[(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]norbornane:To a 3-necked, 500-mL round bottomed flask equipped with a condenser(nitrogen inlet), digital thermometer and magnetic stir bar was added173.2 g (0.63 mol) of5-[(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]-2-norborneneand 100 g (1.9 mol) of formic acid (88%) and the mixture heated at 100°C. under nitrogen overnight. The resulting yellow solution wasevaporated on a rotary evaporator leaving a thick yellow oil to whichwas added 120 mL of concentrated ammonium hydroxide (28%) and themixture heated with stirring at 60° C. overnight. After cooling, thelayers were separated and the lower layer was diluted with 500 mL ofdiethyl ether and washed sequentially with 5% (v/v) HCl (2×250 mL),water (2×200 mL) and brine. The ether solution was dried over MgSO₄,evaporated and distilled at 92° C. at 0.8 mm Hg to yield 156 g (84%) ofthe product as a clear, colorless oil.

(b) Synthesis of VE-NBHFA using mercuric acetate: In a dry 250 mLround-boftom flask equipped with a stir bar, condenser, and nitrogeninlet2-hydroxy-5-[(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]norbornane(20.5 g, 70 mmol), ethyl vinyl ether (140 mL), mercuric acetate (1.5 g,4.7 mmol), and triethylamine (1.3 mL, 9.4 mmol) were placed. Thereaction mixture was heated to 50° C. and stirred for 53 hrs (26 hrssufficient by GC). The mixture was then cooled to room temperature andpoured into a 500 mL separatory funnel containing brine. The resultingmixture was extracted four times with diethyl ether. The combinedorganic extracts were dried over MgSO₄ and the solvent was removed bydistillation under reduced pressure. Vacuum distillation (87-88° C., 7mmHg) (sodium bicarbonate, 70 mmol was added to batch to preventoligomerization) afforded 8.2 g of colorless liquid.

EXAMPLE 4 Scaled-Up Synthesis of VE-NBHFA

To a 1-L, 3-necked round bottomed flask equipped with a nitrogen inlet,digital thermometer and magnetic stir bar was added 100 g (0.34 mol) of2-hydroxy-5-[(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]norbornane(prepared in part (a) of Example 3), 400 g (5.5 mol) of ethyl vinylether and 3.2 g (0.01 mol) of mercuric acetate and the solution stirredat room temperature for 2 days. The mixture was evaporated on a rotaryevaporator, diluted with 500 mL of diethyl ether and washed sequentiallywith saturated sodium bicarbonate, water and brine. After stirring overanhydrous magnesium sulfate overnight, the suspension was filtered, thesolvent removed on a rotary evaporator and the resulting oil distilledtwice from solid sodium bicarbonate at 96° C. @ 0.5 mmHg. The bestfractions were pooled to yield 54 g (50%) of the product as a clear,colorless oil.

EXAMPLE 5 Synthesis of TBTFMA/VE-PrHFA Copolymer

Radical copolymerization of t-butyl 2-trifluoromethylacrylate (TBTFMA,0.55 g, 2.8 mmol) with VE-PrHFA (0.71 g, 2.8 mmol) was carried out at60° C. for 14 hrs in N₂ after deaeration, using AIBN (0.04 g, 0.2 mmol:4.0 mol %) as the initiator in ethyl acetate (5.6 mL). The copolymer waspurified by repeated precipitation in hexane and dried in a vacuum ovenat 60° C. overnight (Yield 61%). The composition of the resultingcopolymer was found to be TBTFMA/VE-PrHFA=68/32 by ¹⁹F NMR (M_(n)=10645,M_(w)=16616, M_(w)/M_(n)=1.53, T_(g)=89° C.).

EXAMPLE 6 TBTFMA/VE-NBHFA Copolymer

Radical copolymerization of TBTFMA (7.8590 g, 40 mmol) with VE-NBHFA(12.7388 g, 40 mmol) was carried out at 60° C. for 19 hrs in N₂ afterdeaeration, using AIBN (0.05256 g, 3.2 mmol: 4.0 mol %) as the initiatorin bulk. The mixture solidified in 30 min. The copolymer was purified byrepeating precipitation twice in hexanes and dried in a vacuum oven atroom temperature overnight (Yield>41%). The composition of the resultingcopolymer was TBTFMANE-NBHFA=63/37 by ¹⁹F-NMR (M_(n)=8943, M_(w)=17169,M_(w)/M_(n)=1.92, T_(g)=124° C.).

EXAMPLE 7 TFMA-NBHFA/VE-PrHFA Copolymer

Radical copolymerization of TFMA-NBHFA (4.1872 g, 10 mmol;TFMA=α-trifluoromethylacrylate) with VE-PrHFA (2.5298 g, 10 mmol) wascarried out at 80° C. for 24 hrs in N₂ after deaeration, using AIBN(01325 g, 4.0 mol %) as the initiator in ethyl acetate (EtOAc) (60 g).The copolymer was purified by repeated precipitation in hexanes anddried in a vacuum oven at room temperature overnight (Yield>51%). Thecomposition of the resulting copolymer was determined to beTFMA-NBHFA/VE-PrHFA=64/36 by ¹⁹F and ¹³C NMR (M_(n)=17690, M_(w)=32149,M_(w)/M_(n)=1.82, T_(g)=76° C.).

EXAMPLE 8 TFMA-NBHFA/VE-NBHFA Copolymer

Radical copolymerization of TFMA-NBHFA (4.1977 g, 10 mmol) with VE-NBHFA(3.200 g, 10 mmol) was carried out at 60° C. for 24 hrs in N₂ afterdeaeration, using AIBN (0.1346 g, 4.0 mol %) as the initiator in EtOAc(5.015 g). The copolymer was purified by 2× precipitation in hexane anddried in a vacuum oven at room temperature overnight (Yield>62%). Thecomposition of the copolymer was TFMA-NBHFA/VE-NBHFA=61/39 by ¹⁹F NMR(M_(n)=5609, M_(w)=7864, M_(w)/M_(n)=1.40, T_(g)=1 25° C.).

EXAMPLE 9 TBTFMA/TFMA-NBHFA/VE-PrHFATerpolymer

Radical terpolymerization of TBTFMA (1.9645 g, 10 mmol), TFMA-NBHFA(2.0846 g, 5 mmol), and VE-PrHFA (2.5236 g, 10 mmol) was carried out at60° C. for 21 hrs in N₂ after deaeration, using AIBN (0.1640 g, 4.0 mol%) as the initiator in EtOAc (1.00 g). The copolymer was purified by 3×precipitation in hexanes and dried in a vacuum oven at room temperatureovernight (Yield>83%). The composition of the terpolymer was determinedto be TBTFMA/TFMA-NBHFA/VE-PrHFA=41/23/36 by ¹³C NMR (M_(n)=58674,M_(w)=439974, T_(g)=71° C.).

EXAMPLE 10 TBTFMA/TFMA-NBHFA/VE-NBHFA Terpolymer

Radical terpolymerization of TBTFMA (1.9654 g, 10 mmol), TFMA-NBHFA(2.0942 g, 5 mmol), and VE-NBHFA (3.1889 g, 10 mmol) was carried out at60° C. for 24 hrs in N₂ after deaeration, using AIBN (0.1648 g, 4.0 mol%) as the initiator in EtOAc (3.0 g). The terpolymer was purified byrepeating precipitation twice in hexanes and dried in a vacuum oven atroom temperature overnight (Yield>56%). The composition of theterpolymer was determined by ¹³C NMR to be 50/24/26 (M_(n)=4416,M_(w)=6605, M_(w)/M_(n)=0.37, T_(g)=123° C.).

EXAMPLE 11 Resist Formulation Prepared with TBTFMA/TFMA-NBHFA/VE-NBHFATerpolymer

A chemical amplification resist was formulated from the terpolymer ofExample 10 (TBTFMA/TFMA-NBHFA/VE-NBHFA, OD of 2.1/μm at 157 nm) byadding the polymer to propylene glycol methyl ether acetate (PGMEA),followed by bis-(t-butylphenyl)iodonium perfluorooctanesulfonate (IPFOS)(4 wt. %) and tetrabutylammonium hydroxide (TBAH, 0.2 wt. %). The resistwas spin-coated onto a silicon wafer or onto an antireflective coating(e.g., AR19), soft-baked at 130° C. for 60 seconds, exposed to 193 nmradiation using an ISI 193 Mini-stepper and a chrome-on-glass mask,post-exposure baked at 140° C. for 60 seconds, and then developed with a0.26 N TMAH aqueous solution. FIGS. 1A and 1B are SEM photosillustrating the excellent resolution obtained, 130 nm lines/space (L/S)and 120 nm L/S patterns printed with the resist formulation.

EXAMPLE 12 Resist Formulation Prepared with a Blend ofPoly(TBTFMA₆₀/VE-NBHFA₄₀) Copolymer and NBHFA Homopolymer (PNBHFA)

A chemical amplification resist was formulated from a blend ofpoly(TBTFMA₆₀/VE-NBHFA₄₀) (as may be prepared according to Example 6)and PNBHFA by mixing the polymers at a 1:1 ratio in propylene glycolmethyl ether acetate (PGMEA), followed by addition of IPFOS (4 wt. %)and TBAH (0.2 wt. %). The resist was spin-coated onto silicon wafers,soft-baked at 130° C. for 60 seconds, exposed to 193 nm radiation usinga chrome-on-glass mask, post-exposure baked at 140° C. for 60 seconds,and then developed with a 0.26 N TMAH aqueous solution. FIGS. 2A, 2B,2C, and 2D are SEM photos showing the dense (120 nm L/S) patternsprinted with the resist formulation (corresponding to 30.0, 29.4, 28.8,and 28.2 mJ/cm²). FIG. 3 is an SEM photo of an analogous patterned blendresist prepared as above but employing a 157 nm exposure step (using anExitech 157 nm tool, NA=0.85), and is also indicative of superiorresolution.

The results obtained contrasted markedly with earlier formulations basedon trifluoromethylacrylate copolymers and on blends of such copolymerswith PNBHFA, which exhibited significant adhesion failure on bare Si. Inaddition, only the aforementioned blends enabled effective printing.

1. A fluorinated vinyl ether having the structure